I. Field
The following description relates generally to wireless communications, and more particularly to employing interference-overload indications to yield pilot strength reports that can be leveraged to mitigate reverse link interference experienced at base station(s) in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT, NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
An access terminal can utilize a channel in which base stations of different power levels operate. For instance, the access terminal can be served by a particular base station, while one or more other base stations can be positioned in vicinity of the access terminal. The one or more other base stations can include a femto cell base station that can transmit over a forward link at a much lower power than disparate base stations (e.g., macro cell base stations, . . . ); due to the lower forward link transmit power, the access terminal can be unaware of the presence of the femto cell base station. Additionally or alternatively, the one or more other base stations can include a base station that is part of a private enterprise, which denies access to access terminals not belonging to a private group.
According to an example, an access terminal can communicate with its serving base station while in vicinity of pico cell base station(s) (e.g., cellular base station(s) that each cover a relatively small area such as in-building or in-aircraft) or femto cell base station(s) (e.g., cellular base station(s) that each cover a relatively small area such as in a residential or small business environment) and/or base station(s) that deny access to the access terminal. For instance, the access terminal can be unaware of a pico or femto cell base station due to low forward link transmit power employed thereby. Whether operating in vicinity of pico/femto cell base station(s) and/or base station(s) that deny access, the access terminal can cause significant interference to these other base stations since the access terminal can be closely positioned to the other base stations. Further, when employing conventional techniques, interference resultant from reverse link transmission by the access terminal can commonly be uncontrolled when the pico/femto cell base station(s) and/or base station(s) denying access are excluded from an active set of the access terminal. In these situations, such uncontrolled reverse link interference can degrade overall system performance.